Stethoscope



D. LITTMANN Oct. 29, 1963 sTETHoscoPE 1 Filed June le, 1960 FIGA I @a/ff INVENTOR. W

Belmont, Mass.

Filed dune 16, 196i), Ser. No. 36,641 Ciaims. (Cl. 181-24) The present invention relates to a stethoscope and more particularly to an improved form of a binaural stethoscope.

Most stethoscopes currently in use are formed with a pair of rigid ear tubes interconnected by a flexible Y member. An external spring arrangement spring tensions the ear tubes towards one another so that they may freely grip the wearers head. This type of construction is cumbersome and bulky.

Several modifications have been made to improve such structures by integrally forming the spring member with the Y-shaped interconnecting tube. Such modifications, however, have not been satisfactory for several reasons.

For example, the material utilized to form the exible tl-shaped tube has been unsuited for prolonged use and does not lend itself to an integral structure of the type contemplated. Furthermore such modifications are ditiicult to manufacture.

ln addition to these problems, the flexible Y-shaped interconnecting sound tubes used to connect the ear tubes and a chest piece or receiver will crack at the junction of the stem of the Y and the two arms with constant flexing.

The present invention is designed to overcome these problems by providing an integral stethoscope having two ear tubes interconnected by a synthetic resin flexible Y-shaped sound tube. The stern of the Y is formed integrally with a helical spring means adapted to prevent cracking at the base of the stem after prolonged amounts of flexing. The exible arms of the Y sound tube are formed with a leaf spring tensioned within the tube adapted to tension the arms towards one another. The receiver of the stethoscope is formed with a dual receiver having novel means for connecting one of two microphones to the sound tube.

The present invention also provides a unique method of assembly of stethoscopes of the type described. In this method the ear tubes are rigidly secured to the end of an interconnecting leaf spring. These joined elements are then partially threaded through the arms of the Y-shaped sound tube until the ear tubes are symmetrically arranged. The remaining components are then conventionally assembled.

These and other objects and advantages of the present invention will be more clearly understood when considered in conjunction with the accompanying drawings, in which:

FIG. l is a perspective view of the stethoscope;

FIG. 2 is a cross sectional fragmentary view on an enlarged scale of a portion ofthe stethoscope.

FIG. 3 is an exploded detail of adjacent ends of an arm and spring;

FIG. 4 is a fragmentary perspective view on an enlarged scale of the receiver; and,

FIG. 5 is a fragmentary cross section taken along line 5-5 of FIG. 4.

As best illustrated in FIG. l and FIG. 2, a pair of ear tubes 1 and 2 are secured together by a prestressed leaf spring 3 integral with a Y-tube 4. A receiver 5 is secured to the lower end of the stem 6 of the Y tube 4. The ear tubes 1 and 2 have ear plugs '7 and 8 secured respectively to their upper ends. The upper ends are bent as illustrated at 9 and 10 to suitably permit insertion of the ear plugs in the wearers ears. The ear tubes are preferably formed of a stainless steel with an outer diameter of United States Patent O approximately '/16 of an inch and with a .018 inch wall. The length may be varied but preferably should be approximately 7 inches. The lower ends of the ear tubes are rigidly secured to the ends of the spring 3. The spring 3 is formed of high carbon spring steel having a Rockwell hardness of approximately iO-45. This spring 3 is prestressed to form an arc of substantially The leaf is flared at both ends as illustrated at 11 in FIG. 3. These flared ends are rolled over to rigidly engage the shoulder sections 12 formed at the bottom end of each of the ear tubes 1 and 2. The flared end 11 of the spring 3 is crimped about this shoulder section 12. A dimple 13 formed in the shoulder section projects outwardly through a slot 14 formed between the free edges of the flared end to prevent rotation of the tube relative to the spring. A suitable metal to metal adhesive is used to additionally secure the ear tube to the spring in a rigid relationship. Each of the ear tubes is similarly secured to the ends of the spring 3.

The spring is longitudinally positioned in the arms 16 and 17 of the Y tube 4. These arms 16 and 17 form continuous passages with the ear tubes 1 and 2 and form a continuous passage with the stem 6. The Y tube is preferably formed of a polyvinyl chloride acetate.

A helical spring 5t) preferably formed of .016 inch stainless steel wire, having an outer diameter of preferably approximately .026 inch, is integrally molded within the upper end-0f the stem 6 immediately adjacent the junction of the arms 16 and 17. lt has been found that the combination of the polyvinyl chloride acetate Y tube and the leaf spring add substantial and prolonged resilience to the combination.

The lower end of the stern 6 is sleeve fitted to the tubular shaft 2d of the receiver. The sleeve fit is suiiiciently tightened as to permit rotation of the tubular shaft with rotation of the adjacent portion of the stem 6.

This tubular shaft 20 is rotatably interengaged with the diaphragm microphone 22 and open microphone 21 of the receiver 5. These microphones 21 and 22 are integrally formed with the body of the receiver of a suitable steel. The open microphone 21 is of conventional bell shape having a relatively narrow diameter but deep cup 24. An opening 23 at the cup apex is adapted to be aligned with an opening 25 in the tubular shaft 2t) when the tubular shaft 2t) is rotated. The diaphragm microphone 22 has a greater diameter than the open microphone and is formed with a suitable diaphragm 26 anchored at its periphery by suitable lip means 27 to the periphery of the diaphragm microphone cone 28. The diaphragm microphone 22 is formed with an opening 29 at its apex adapted to be aligned with the opening 25 in tubular shaft 2t). FIG. 4 illustrates the microphone in this position.

The tubular shaft 20 ts Within a cylindrical recess formed between the two microphones 21 and 22 as illustrated in FIG. 5. It is secured against axial movement by means of the retaining ring 35, FIG. 4, which engages a shoulder in the outer wall of the tubular shaft 20.

The tubular shaft Z0 is adapted to rotate around a full 360 but snaps into two selected positions which locate the opening 25 in aligment with either the opening 29 or the opening 23 for connections of one of the two microphones 21 and 22. This snap fastening is actuated by the spring arrangement illustrated generally at 40. In this spring arrangement, a U-shaped spring or spring detent 41 having an enlarged bight section 42 is positioned at the lower end of the shaft 20. This spring 41 has its upper ends 43 positioned within the shaft 20 in locked or fixed engagement with its side walls. The enlarged bight portion 42 projects outwardly beyond the shaft 20 and is adapted to engage the diametrically opposite grooves 44, FIG. 5, formed in the wall which forms the 3 cylindrical recess within which the tubular shaft 2) is located. n rotation of the' tubular shaft 2t? relative to the microphones 21 and 22, the spring 4t? is forced from the grooves under tension until the microphones are rotated a full 180 relative to the shaft 20, at which point the spring reengages the grooves 44.

ln the assembly of this structure, the ear tubes 1 and 2 are first rigidly connected at their ends to opposite ends of the spring 3. The flared ends 14 are bent over and engaged to shoulder 12 and the structure iis thereafter cemented to form a more rigid joint of the tubes 1 and 2 with the spring 3. Before insertion of the ear pieces on the free ends of the ear tubes 1 and 2i, the series joined ear tubes and springs are threaded through the arms 16 and 17 of the Y tube 4 unti'l the Y tube is symmetrically located with respect to the tubes Y1 and -2 in the position generally illustrated in FIG. 2. The ear pieces are then attached as illustrated in FIG. 1 and the receiver is sleeve fitted to the free end of the stem 6. The helical spring t) is preferably molded into lthe Y tube before the assembly as described above takes place.

What is claimed is:

l. In a stethoscope construction having a pair of rigid elongated ear tubes and a flexible Y tube with integral arms and a stem, an elongated leaf spring positioned within said Y tube arms and prestressed to form an arc of substantially 180 and having flared ends, means forming shoulder sections at one end of each of said ear tubes and dimples in said shoulder sections, said flared ends Wrapped around said shoulder sections with the edges of said ilared ends engaging said dimples to prevent relative rotation of said ear tubes and leaf spring.

2. In a stethoscope construction having a pair of rigid elongated ear tubes and a flexible Y tube with integral arms and a stem, an elongated lleaf spring positioned within said Y tube arms and prestressed to form an arc 21 of 180, having means rigidly interengaging ends of said ear tubes Iwith the ends of said leaf spring, and a helical spring coaxial with and positioned in said stem with one end adjacent the intersection of said Y tube arms and said stem.

3. A structure as set forth in fclaim 2 wherein said helical spring is integrally formed with the inner wall of said stem.

4. In a structure as set forth in claim 2 wherein said Y tube is formed of a polyvinyl chloride acetate resin having an outer diameter of substantial-1y 5A@ inch and an inner diameter of substantially PAG inch and wherein said spring is formed of a high carbon spring steel substantially .025 inch thick with a Rockwell hardness of between substantially to 45.

5. In a l stethoscope having means mounting a diaphragm, the combination comprising a Y-shaped ilexible tube having a pair of legs and a stem, said stem connected to said means, a pair of elongated rigid tubes each having an ear piece at one end and projecting into the free end of a leg at the other end, a leaf spring prestressed into substantially a U-shaped configuration and positioned within said legs and means rigidly securing said Y spring to the other ends of said rigid tubes 'including complementary elements on the ends of said ear tubes and spring adapted to prevent relative rotation and thereby secure said ear pieces in relative orientation to one another.

References Cited in the file of this patent UNITED STATES PATENTS l1,096,024 Durand May l2, 1914 1,585,407 Morin May 18, 1926 2,142,407 Norton et al. Ian. 3, 1939 2,719,594 Smithline Oct. 4, 1955 2,722,989 Tynan ...t Nov. 8, 1955 

2. IN A STETHOSCOPE CONSTRUCTION HAVING A PAIR OF RIGID ELONGATED EAR TUBES AND A FLEXIBLE Y TUBE WITH INTEGRAL ARMS AND A STEM, AN ELONGATED LEAF SPRING POSITIONED WITHIN SAID Y TUBE ARMS AND PRESTRESSED TO FORM AN ARC OF 180*, HAVING MEANS RIGIDLY INTERENGAGING ENDS OF SAID EAR TUBES WITH THE ENDS OF SAID LEAF SPRING, AND A HELICAL 